"We used additional Police officers who were in the area to help us cordon off the school so we could catch the perps," the post said.
"Needless to say, we were very surprised when we rounded a corner and found a young couple in the early stages of a 'rendezvous'!"
The pair were asked to move on from the school grounds.
"Once they were re-clothed they were kindly asked to move their show elsewhere," Cambridge Police wrote, adding the #betterworkstories hashtag.
And Facebook users enjoyed the tale, tagging friends and having a laugh.
"I bet they had red cheeks," wrote one user, prompting police to respond: "Yeah, we weren't looking that closely!"
"Learnt something at school today," wrote another.